Control knob for condensers



Juiy 21,1931.

T. J. SCOFIELD CONTROL KNOB FOR QONDENSERS Filed OcLBO. 1929 INVENTOR 772 dare J: cofz/d TIORNEY gripped sciently to 5- July 21, 1931 rro SATES PATENT orFicE 130R comm, A. ,conronuron or one common canon son connmrsmas Application mes October so, 1929. Serial R0. 403,529.-

This invention relates to construction of control hobs for condrs used in radio sets and similar devices.

An object of the invention is to construct s. control lmob thst may be re e plied d removed from the end of a. sha of a condenser or similsr device while being piece.

Another object of the invention is to construct control @obs 8. cheap and sstisfactory manner. 1

Other objects will appear in the following description, reference being bad to the drawin in which:

ig. 1 is an elevation of the end of the shaft of e uni-control condenser such as used iii-radio receiving sets and similar devices.

held in position on Pg 2 is s. top view of the end of the shaft sho in Fig. l.

Fig. 3 is an end view of the shafts shown in Figs. 1 and 2 with the bail or key removed.

Fig. 4 is c section of the control knobin position to be pushed on to the shaft in interocking relation therewith.

Fig. 5 is o sectional view showing the knob the shaft by the bail.

Fig. 5 is on end view of the apparatus of Pi f).

ig. 7 is s view of a modification.

The sheft 1 shown in l i 1 may be the control sheft of a uni-,contro gang condenser or of s rheostet inductance control potentiometer or other adjustable erraent useful in radio receiving sets or other simiindevices. The shaft 1 hes s hole 2 therein edjecent to the end end fitting in this hole is e. wire beil 3 adapted tosct es s key. The beil mey melee s. snug fit with the it msy be somewhat smaller. e end of the sheft i has the periphery notched at 4.- and pushed downward until it snaps into'the notches d and 5 in the position shown in .A 2

normally remain in and attsching means in hole 2 or.

- usual in control knobs-for present day receiving sets. This knob has an extension 7 which has a central hole 8 with grooves 10, 11, 12 and 13, more clearly shown in Fig. '6. Only two of these grooves, of course, are necessary to fit on to the bail, but for ease in finding the proper position when inserting the knob it is preferable to make more than two of the grooves.

After the bail is in position on the end of the shaft, as shown in Fig. 2, the gang condenser, resistor, inductance, potentiometer, or other device fastened to the end of the rod may be placed imposition in the radio set or other device and the end of the rod 1" \T. 800, 0] JACKSON, mCHlIGAN, ASSiIGNOB-"IO THE SPARK? WI'I'EING- readily extended through the front panel or,

side of the device. The knob 6 can then be pushed on to the end of the shaft in the position shown in'Fig. 5. It will be seen rom this figure that the spring bail has the ends forced downward into the hole 2 and the tension in the spring forces the horizontal portions of the bail against the bottom of grooves 10 and 12. The bail is also forced against the sides of the grooves as shown at 13 and 14 in Fig. 6. There is'therefore a double spring tension tendin to produce frictional contact between the bail, the rod and the knob. This is suficient ho hold the knob in position yet it permits it to be easily and bottom of the slots is secured by bending the bail as at 15.

In prior arrangements of this sort the frictional contact has been entirely produced by a horizontal portion such as at 10 and 12. This has been insufiicient to hold the shaft in position and I have found the combined sldewise and radial tension has remedied the defects. Also prior arrangements s1m1-' lar to these the key has been free to pass over the end from'top to bottom in the position shown in Fig. 1 and it will not stay In position for proper insertion of the knob. By

providing the notches 4 and 5 and by givin sufiicient compression of the bail at the mi portion the bail will snap into these notches and stay in that position when the end of the shaft is be' inserted through the panel, in fact it w' stay in osition until it 7 is intentionally snapped out or some reason or other. Control knob adjustments made in accordance with this invention have been quite successful in operation and the cost has been quite low. Devices fastened together in 10 this way continue to hold in a'sat1sfactory manner without loss of gri ping action irrespective of the number 0 times that they may be attached or detached.

A further advantage in arrangements of i this sort is that a knob may be removed from the shaft without there-being any liability of the key dropping out of (position as is the case with ordinary key an spline arrangement's. H I

Having described my invention, what I claim is: s

1. A control shaft' member having transverse openings, a spring bail member 'having its ends secured in s'aid'o nings, and a control knob having grooves t erein adapted to fit over the end of said shaft and bail one of said members having means'to cause the bail to be held in frictional contact with the ,bottom'and side of each of said grooves. 2. A control shaft having diametrically ositioned transverse openings, and notches in the periphery of its end separated from each other by'arcs of unequal length, a spring bail having its ends secured in said openings and a middle portion fitting into each of said notches to hold the b'ail at a-slight angle to 'the axis of the shaft,'and a control member having 4 ooves therein adapted to fit over the said ail when the said member is in po- 40 sition on the end of the shaft whereby said bail tends to expand diametrically of the shaft against the bottom of the said groove and also to press against the sides of the groove tangentially of the shaft. 3. A control shaft having transverse-openings, and notches in the periphery of its end,

a spring bail having its end secured in said 7 openings and middle portions fitting into each of said notches, a control member havmg'grooves therein and adapted to fit over the end of the shaft, the center of said grooves being positioned slightly out of alignment with the center of said bail wher'eby the bail tends to press outwardly. against the bottom of the grooves and against the sidesof the grooves tangentially of the shaft. In testimony whereof, I have si ed my name to'this specification this 2211 day of October, 1929. 1 THEODORE J. SCOFIELD. 

